The present invention relates generally to methods of making shaped three-dimensional products from microporous expanded polytetrafluoroethylene. More particularly, the present invention relates to a method of shaping three-dimensional products by manipulating an expanded polytetrafluoroethylene tubular body into a desired three-dimensional conformation. The present invention entails radially expanding a longitudinally expanded polytetrafluoroethylene (ePTFE) tube to form a radially expanded ePTFE (rePTFE) tube, engaging the rePTFE tube circumferentially about a shaping mandrel, heating the assembly to a temperature below the crystalline melt point temperature, or sintering temperature, of polytetrafluoroethylene to radially shrink the diameter of the rePTFE tube into intimate contact with the shaping mandrel, and heating the assembly to a temperature above the crystalline melt point temperature of polytetrafluoroethylene to amorphously lock the microstructure of the shaped polytetrafluoroethylene body.
The three-dimensional shaped microporous expanded polytetrafluoroethylene products made in accordance with the method of the present invention are particularly well suited for use as medical implants, and are particularly useful as venous or arterial prostheses either as vein or artery replacements, as endovascular liners, arterio-venous shunts, or as venous access grafts. As arterial or venous prosthesis, shaped microporous expanded polytetrafluoroethylene grafts have been made which have a flanged cuff section contiguous with an elongate tubular section. The cuffed prosthesis are particularly well suited for use in end-to-side anastomoses such as that required in femoro-popliteal bypass procedures where the flanged cuff section is sutured about an open arteriotomy to form the end-to-side anastomosis. As endovascular liners, the shaped expanded polytetrafluoroethylene products may be configured to have a taper along its longitudinal axis, with a proximal end having either a larger or smaller inner diameter than the distal end, or may have a step taper, where there is a tapered transition zone between two different inner diameter sections, or the product may be configured to have an intermediate section of a larger diameter than proximal or distal ends of the product, or the product may be configured into a bifurcated or trifurcated graft where each of the legs is formed from appropriately sized appendage sections of a base tubular graft member.